* The characters in this story are fictional. However the data are real. The story is set on 27 July 2008 when an air quality warning was issued in Brussels.

Anna is 37 years old and lives in the centre of Brussels. She and
her young son Johan are planning a trip outside the busy city. Anna
suffers from asthma and her doctor has warned of the dangers of air
pollution, especially on hot summer days.

Anna has heard about the London fogs of the 1950s that killed
2 000 people in one week. She has childhood memories of evening
news bulletins showing dead fish and dying trees as '
acid rain' first came to popular attention in the 1970s.

Motherhood and a recent asthma attack have quite rightly brought air
pollution back to mind. The fact is that emissions of many air
pollutants have fallen substantially across Europe since Anna's
childhood. The air she and Johan breathe is much improved compared to
the past, and air policy is one of the great success stories of the
EU's environmental efforts. In particular, EU policy has dramatically
cut emissions of
sulphur, the main component of 'acid rain'.

In contrast,
nitrogen — also a major component of 'acid rain' — has not been
dealt with to the same extent and so continues to cause major problems.
A significant proportion of Europe's urban population still live in
cities where EU air quality limits, protecting human health, are
regularly exceeded. Each year, many more people die prematurely from
air pollution in Europe than die in traffic accidents.

The European goal of achieving levels of air quality that do not
damage people's health or the environment has still not been reached.
EEA analysis suggests that 15 of the 27 EU Member States will miss one
or more of their legally binding 2010 targets to reduce harmful air
pollutants.

Particulate matter and ozone

Two pollutants, fine
particulate matter and
ground-level ozone, are now generally recognised as the most
significant in terms of health impacts. Long-term and peak exposure can
lead to a variety of health effects, ranging from minor irritation of
the respiratory system to premature death.

Particulate matter, a term used to describe a variety of tiny
particles from sources such as vehicle exhausts and domestic stoves,
affect the lungs. Exposure can harm people of all ages, but people with
existing heart and respiratory problems are particularly at risk.

According to the latest EEA data, since 1997 up to 50 % of
Europe's urban population may have been exposed to concentrations of
particulate matter above the EU limit set to protect human health. As
much as 61 % of the urban population may have been exposed to
levels of ozone that exceed the EU target. It has been estimated that
PM2.5 (fine particulate matter) in air has reduced
statistical life expectancy in the EU by more than eight months.

The EEA has noted that while emissions of these two key air
pollutants have dropped since 1997, measured concentrations in the air
we breathe have remained largely the same. As yet, we don't know why
there has not been a drop in ambient concentrations but it could be a
combination of several factors: increased temperatures caused by
climate change could be affecting air quality; perhaps we are on the
receiving end of pollution from other continents or natural emissions
of ozone forming substances released from trees, for example.

A day in the country

Anna is planning a day in the country with Johan. Before leaving her
apartment she logs onto IRCEL, a government web service
providing a host of regular information on air quality around Belgium.
Using maps, Anna can scan readings and forecasts for particulate
matter, ozone, nitrogen dioxide, sulphur dioxide among many others. The
data are relayed to the web from monitoring stations around the
country.

Improvements in monitoring and availability of information on air
pollution are another of the success stories of recent years. For
instance, local data on ozone levels are now passed onto the EEA 'Ozone
web' (1) service that provides an overview
of the situation across Europe.

Anna scrolls across a map of Belgium, zooming in on a monitoring
station in the centre of Brussels, less than two kilometres from her
home.

The reading, taken minutes earlier, shows high levels of ozone in
Brussels. Indeed the website forecasts that levels will exceed EU
target values later that day and again the following day (
Figure 1).

Anna leaves her apartment building and makes for the nearest Metro
station, a 10 minute walk away. Out on the street, the full impact of
the city's traffic problems are easy to see — and smell.

Exhaust emissions from cars in the centre of Brussels, and all major
cities, irritate the respiratory tract and eyes and lungs. Anna and
Johan turn into their local train station and head for the
countryside.

Soon, Anna and Johan are entering a national park just outside
Brussels. A sign tells them that they are visiting a
Natura 2000 site — one part of a European-wide ecological network,
set up to secure natural habitats and to maintain the range of plant
and animal life.

Nitrogen

But what's that smell? A tractor is spraying liquid manure onto a
field not far away. This is irritating, Anna thinks, but it's also part
of real country life which is shown in a rather more romantic way in
Johan's picture books.

The pungent smell is caused by as many as 40 different chemical
substances emitted from the manure. Ammonia (NH3), a
volatile nitrogen compound, is one of them. In very high concentrations
NH3 is caustic and can damage the respiratory tract.
However, the levels here are not dangerous for human health. Anna can
breathe a sigh of relief, albeit a stinky one.
Nitrogen is an essential nutrient in nature. Reactive nitrogen forms
are actually used by our bodies to produce proteins. However, excess
nitrogen can lead to severe environmental and health problems.

'Acid rain' forms when high levels of sulphur and nitrogen oxides
are present in the air. One of the great success stories of air
pollution policy over the last decades has been the massive reduction
in emissions of sulphur dioxide. The 32 EEA member countries
reduced sulphur emissions by 70 % between 1990 and 2006. Nitrogen,
on the other hand, has not been dealt with as successfully.

With sulphur emissions declining, nitrogen is now the principal
acidifying component in our air. Agriculture and transport are the main
sources of nitrogen pollution. Agriculture is responsible for more than
90 % of ammonia (NH3) emissions alone.

Suddenly Johan, who has been walking unsteadily loses his balance
and falls into a clump of stinging nettles. Having picked him up and
brushed him off, Anna notices nettles everywhere. She has vivid
memories of them as a child in a neighbour's garden. Then the nettles
grew around a compost heap that was also used as a dump for poultry
dung. That was no coincidence — the stinging plant is an indicator of
high nitrogen concentrations in soils.

'Eutrophication' is the most likely cause of this explosion of
stinging nettles surrounding Johan. It occurs when too many chemical
nutrients (such as N) are available to an ecosystem either on land or
in water. In water, excessive plant growth and subsequent decay occur,
which in turn leads to further effects including oxygen depletion. Fish
and other animals and plants ultimately suffocate as the oxygen supply
is used up.

The abundance of the nettles here suggests that despite being a
protected habitat, the Natura 2000 site is not immune from airborne
nitrogen deposits. The fence protecting the area offers no defence — in
fact building a greenhouse around the area would be the only way to
protect it totally from airborne substances.

Looking ahead

Because air pollution pays no regard to national boundaries the
problem needs to be tackled internationally. The United Nations
Convention on Long-range Transboundary Air Pollution (LRTAP Convention)
agreed in 1979, has been signed by 51 countries and forms the basis of
the international fight to tackle air pollution.

In parallel, the EU has developed polices limiting the total
emissions of each Member State, setting legally binding limits. The '
National Emissions Ceiling Directive' (NECD) is a key
EU policy. It sets 'ceilings' or limits for four pollutants:
sulphur dioxide (SO2), nitrogen oxides (NOx),
non-methane volatile organic compounds (NMVOCs), and ammonia
(NH3). Member States should meet these ceilings by 2010.

The EEA considers that further emission cuts are still needed in
order to properly protect environment and health. An EEA analysis of
the most recent NECD data (2) indicates that 15 Member States expect
to miss at least one of their four ceilings; with 13 anticipating
missing ceilings for the 2 nitrogen-containing pollutants
NOX and NH3(3).

In 2009 the European Commission plans to publish a proposal to
revise the current NECD, including stricter ceilings for the year 2020.
National limits are likely to be proposed for fine particulate matter
(PM2.5) for the first time.

The NECD is mirrored by air quality directives setting limit and
target values for major air pollutants. A new one called the Cleaner
Air For Europe (CAFE) Directive was adopted in April 2008. For the
first time it sets legally binding limit values for PM2.5
concentrations (fine particulate matter), to be attained in 2015. The
European Commission is also taking countries to task for having missed
earlier limits and, where sufficient measures have not been outlined to
improve performance, has begun infringement proceedings.

Later that evening Anna, while watching the evening news, sees that
an air quality warning has been issued by the government in response to
high ozone levels beyond the EU threshold. The warning advises people
with breathing problems to take precautions such as avoiding strenuous
exercise while the ozone levels remain high.

Climate change mitigation efforts will improve air
quality

In January 2008, the European Commission proposed a Climate and
Energy package to:

reduce greenhouse gas emissions by 20 % by 2020;

increase the share of renewable energy by 20 % by 2020;

improve energy efficiency by 20 % by 2020.

The efforts required to meet these targets will also cut air
pollution in Europe. For example, improvements in energy efficiency and
increased use of renewable energy will both lead to reduced amounts of
fossil fuel combustion — a key source of air pollution. These positive
side effects are referred to as the 'co-benefits' of climate change
policy.

It has been estimated that the above package will cut the cost of
meeting EU air pollution targets by EUR 8.5 billion per year. The
savings to the European health services could be as much as six times
that figure.

(2) The
NEC Directive status report (EEA Technical report No 9/2008) documents
the data officially reported by Member States at the end of 2007.

(3) Belgium, France, Germany and the
Netherlands believe that new policies and measures, not yet enacted,
will help them reach their 2010 emissions ceilings. In addition,
several other Member States believe they will over achieve their
original ceilings.